Space launch

Space launch is the earliest part of a flight that reaches space. Space launch involves liftoff, when a rocket or other space launch vehicle leaves the ground, floating ship or midair aircraft at the start of a flight. Liftoff is of two main types: rocket launch (the current conventional method), and non-rocket spacelaunch (where other forms of propulsion are employed, including airbreathing jet engines or other kinds).

Issues with reaching space

Definition of space

Space has no physical edge to it as the atmospheric pressure gradually reduces with altitude; instead, the edge of space is defined by convention, often the Kármán line of 100 km. Other definitions have been created as well, in the US for example space has been defined as 50 miles.

Energy

Therefore, by definition for spaceflight to occur, sufficient altitude is necessary. This implies a minimum gravitational potential energy needs to be overcome: for the Kármán line this is approximately 1 MJ/kg. W=mgh, m=1 kg, g=9.82 m/s², h=10⁵m. W=1*9.82*10⁵≈10⁶J/kg=1MJ/kg